Electric discharge tube



Feb. 12, 1929. 1,701,849

G. HOLST ET AL ELECTRIC DISCHARGE TUBE Filed July 28, 1923 Patented Feb. 12, 1929.

UNITED STATES PATENT OFFICE.

GILLES HOLS'I. AND EKKO OOSTERHUIS, F EINDHOVEN, NETHERLANDS, ASSIGNORS TO NAAMLOOZE VENNOOTSCEAP PHILIPS GLOEILAMPENFABRIEKEN, OF EIND- HOVEIT, NETHERLANDS.

ELECTRIC DISCHARGE TUBE.

Application filed July 28, 1923, Serial No.

The present invention relates to electric discharge-tubes, more particularly it relates to discharge-tubes being provided with an incandescent cathode.

It is known to compose the incandescent cathode of such devices of a highly refractory metal, such as for example tungsten.

According to the present invention incandescent cathodes of discharge-tubes are at least at their surface made of hafnium, i. e. the element the atomic number of which is 7 2. Hafnium is highly refractory and has a low constant of Richardson. The said metal has consequently the advantage that at a. temperature at which the speedof volatilization is exceedingly small it has a very high emission of electrons.

According to the invention, it is also possible to make only the surface of glowca-thodes of discharge-tubes of hafnium. In this case the surface of a. glowing bod of other materials such as tungsten may e covered with hafnium.

Discharge-tubes with glowcathodes accordin r to the invention are quite suitable for use as -ray tubes, rectifiers, receivingand generating tubes or amplifiers for wireless telcgraphy and telephony and other purposes.

The accompanying drawing shows a discharge-tube with three electrodes, viz an incandescent cathode, an anode and a grid, such as are generally applied as receivers or amplifiers for wireless telegraphy, telephony or other purposes.

In the drawing a closed envelope 1 which may consist of glass or the like is provided with a stem 9 supporting the electrodes.

The electrodes are concentrically arranged within each other. The anode 2, consisting for example of nickel, is shaped as a nearly closed cylinder and is supported by its current-lead 5. The grid 3 consists of a coiled 654,481, and in France February 21, 1923.

wire of suitable metal, for example nickel or molybdenum and is supported by the currentlead 6; The incandescent cathode, 4 is a wire stretched between current-leads 7 and 8.

The current-leads 5, 6, 7 and 8 are hermetically sealed into the stem 9.

The envelope 1 may be highly evacuated in any known manner.

According to the invention the incandescent cathode 4 may consist of hafnium. It may also consist of acore of a suitable refractory material, having a covering of hafnium; the core may consist for example of tungsten.

What we claim is R 1. An electrode for an electric discharge tube comprising a cathode containing hafmum.

2. An electric discharge tube comprising a cathode thesurface of which contains hafmum. 1

3. In electron discharge tubes, a cathode adapted to emit electrons, said cathode comprising a core of conducting refractory material and a coating of hafnlum.

4. An electron "emitting cathode comprising a filamentary conductor containing hafnium.

5. An electron emitting cathode comprising a filamentary conductor the surface of which contains hafnium.

6. An electron emitting cathode comprising a filamentary conductor having a coating of hafnium.

7. An electron emitting cathode comprising a core of tungsten coated with a film of hafnium.

8. A cathode for electron-discharge devices having the element hafnium as a constituent thereof.

In testimony whereof we aflix our signatures.

GILLES HOLST. EKKO OOSTERHUIS. 

